Zaɓin hannun jari mai ƙarfafawa (ISO) shine "zabin hannun jari da kamfani ke bayarwa ga jami'anta da ma'aikatansa a matsayin nau'in diyya wanda ke ba su damar siyan hannun jari na hannun jarin kamfani a kan ƙayyadadden farashi a cikin ƙayyadadden lokaci kuma wanda ya cancanci kulawa ta musamman ta haraji a ƙarƙashin Code Internal Revenue Code." A wasu kalmomi, ISO wani nau'i ne na zaɓin hannun jari na ma'aikaci wanda ke ba da wasu fa'idodin haraji ga mai karɓa, kuma yawanci ana amfani da shi azaman hanyar ƙarfafawa ko kari ga ma'aikata.